Field of the Invention
Embodiments of the present invention generally relate to an apparatus and method for storing cable in a wellbore.
Description of the Related Art
The installation and operation of permanent control or sensor systems in oil or gas wells (geothermal, CO2 injection wells, etc.) requires the use of cables between the surface of the well and the downhole wellbore equipment for supply of power, control and/or the provision of a conduit for communications. For example, cable may include electrical conductors, hydraulic lines, or fiber optic cables. In most cases, the cable runs along a string of tubulars, like production tubing from downhole equipment to the surface of the well where it extends through a liner hanger or other device that supports the weight of the string. Generally, it is desired to run the cable parallel to the axis of the wellbore tubing with clamps applied to support the cable and hold it parallel to the tubing.
It is also common to provide extra cable at an upper end of the tubing string, just below the liner hanger or tubing hanger, to facilitate access to and service of downhole equipment. The additional cable, known as a “service loop”, facilitates the replacement and rework of the downhole components as it provides personnel with extra cable. In one current technique, it is common to wrap numerous turns of the cable around the tubing in order to store it in the wellbore. In applications involving more than one cable, the cables are wound around the tubing side by side.
There are a number of difficulties associated with providing a service loop as described above. First, the cables are relatively stiff, so they resist being wound around the tubing and tend to “spring back” when released. In some instances, the cable (and any conductors therein) may break if bent beyond its elastic limit. This can require the involvement of multiple rig personnel when winding the cable. In a typical setting multiple individuals hold the excess cable while encircling the tubing numerous times in order to wrap the cable. The cable also has a minimum bending radius beyond which its mechanical integrity is compromised and great care must be taken not to bend the cable beyond this limit. Additionally, care must be taken to assure the cable is tightly wound around the tubing and does not overlap, as slack cable or overlaps increase the probability that the cable will be damaged during run-in. The process of unwrapping the cable is equally complex, as it must be unwound in a controlled manner to avoid entanglement or damage and to assure that any separate cable remaining on the tubing remains securely wound.
There is a need therefore, for an apparatus and method to store cable in a wellbore that overcomes the problems associated with prior art methods and apparatus.